Added a generics test case.

tests/accept/compile/tgenericvariant.nim

@@ -0,0 +1,23 @@
+type  
+  TMaybe[T] = object
+    case empty: Bool
+    of False: value: T
+    else: nil
+
+proc Just*[T](val: T): TMaybe[T] =
+  result.empty = False
+  result.value = val
+
+proc Nothing[T](): TMaybe[T] =
+  result.empty = True
+
+proc safeReadLine(): TMaybe[string] =
+  var r = stdin.readLine()
+  if r == "": return Nothing[string]()
+  else: return Just(r)
+
+when isMainModule:
+  var Test = Just("Test")
+  echo(Test.value)
+  var mSomething = safeReadLine()
+  echo(mSomething.value)